The proposed research seeks to evaluate and investigate an alternative to pesticides for population suppression of the immature stages of Culicides (mosquitoes) that infect man with organisms that cause debilitating diseases such as encephalities, malaria, dengue, filariasis and yellow fever. The efficacy of different species of the fresh-water planarians (Tricladida: Turbellaria) will be investigated as alternative bio-control agents. Specimen will be collected in Mississippi and Louisiana. The proposed study is divided into five phases: (1) laboratory culturing and mass production of planarians by accelerating the process of a sexual reproduction through photoperiod, nutrition, sectioning and other factors (2) predator-prey interaction between five or more species of mature planarians and laboratory and filed population of mosquito vectors (3) an investigation into the larvicidal potential of mucous harvested from planarians b centrifugation and food stimulation (4) degree of tolerance by various species of planarians to different dosage levels of insect growth regulations under laboratory and field conditions (5) field studies in artificial ponds to compare laboratory results. The study will attempt to answer these questions and act as a stimulus for further investigation, aimed at the elimination of mosquito-borne disease which persist as the major, cause of illness and deaths in various parts of the world. For example, there has been a continued outbreak of St. Louis Encephalitis in the Southern portion of this country over the past decade, with more than 2000 cases reported from 30 states in 1975. If the mucous secretion is determined to be a potent larvicide, this indeed, would be a significant breakthrough of public health or biomedical importance. The long-range goal and basic principle of this study should inspire biomedical oriented students and broaden institutional research.